Preheat your oven to 400°F (200°C).
Line a large baking sheet with parchment paper or aluminum foil for easy cleanup.
Prepare the Salmon and Asparagus:
Place the salmon fillets and asparagus on the prepared baking sheet in a single layer.
Drizzle the olive oil over both the salmon and asparagus. Season generously with salt and pepper.
Make the Garlic Butter Sauce:
In a small bowl, combine the melted butter, minced garlic, lemon juice, dill, lemon zest, and red pepper flakes (if using). Mix well to incorporate all ingredients.
Apply the Sauce:
Brush the garlic butter mixture evenly over the salmon fillets.
Drizzle any remaining sauce over the asparagus.
Bake:
Place the baking sheet in the preheated oven.
Bake for 15-20 minutes, or until the salmon is cooked through and flakes easily with a fork, and the asparagus is tender.
Garnish and Serve:
Remove from the oven and garnish with fresh lemon slices and chopped parsley.
Serve immediately, enjoying the rich flavors of garlic butter with tender salmon and asparagus.